I find the Pivot works site a quick and easy way to check bearing sizes for your wheel, but won't tell you if the overall hub width is the same. For that, as far as I know, you got to cross reference hub part numbers and rely on people's experience.

This is a thread I found that shows what wheel's interchange on Yamaha's (Posted by freshy - I guess he's in the know when it comes to wheels!!!):

ok, I'll sum it up for you. Any YZ hub, 125, 250 250F 400 426 450, 1999-2004 will work. The only thing you will run into is that the rotor sizes changed a couple times on both front and back rotors. This will cause the caliper to either foul or not contact enough of the rotor. No problem, if you use the correct rotor. On the rear rim, 125's and 250's use a 1.85" rim rather than the 2.15" found on YZ 250's and 400 426 450's. On the WR series, the hub is also slotted to accept a speedo drive but will work on a YZ or a WR without the speedo drive with a YZ axle spacer in place. By the way I have personally tried a 2004 YZ250F front on my 1999 WR and it does fit.

By TallBoysWRF, Posted March 1, 2006

Forget what I said... I didn't realize you were talking about the 98.

By Yama4Stroker, Posted March 1, 2006

I believe the sprocket inside diameters are larger on the 98 rear hub. A friend of mine ordered a sprocket for a 99 YZ400 on accident, and it didn't fit his 98 YZ400 (luckily I had the 99, so I got it cheap). I also think Yamaha put Excels on in 99+ along with the rear hub change.